Control system for a filtering apparatus

ABSTRACT

A fluidic control system for a filtering device employing a plurality of filters and means for causing a reverse flow through the filters to remove the impurities attached thereto. The control system acts to cause a plurality of rapid release valves to sequentially discharge a reservoir containing fluid under pressure into the filters as a predetermined pressure is attained in the reservoir. A time override control automatically advances the control system to a succeeding release valve if the previous release valve should fail to operate. The control system comprises pure fluidic components which operates without electrical or mechanical connections.

United States Patent 1191 Laliwala May 29, 1973 CONTROL SYSTEM FOR A F ILTERING APPARATUS [73] Assignee: The Carborundum Niagara Falls, N.Y.

[22] Filed: Jan. 4, 1971 [21] Appl.No.: 103,404

Company,

[56] References Cited UNITED STATES PATENTS 3,392,741 7/1968 Shinn ..137/s1.5 3,474,814 10/1969 Sheretal. ..137/s1.s

7/1970 Vanderlip et al. ..55/283 5/1972 Peters et a1 ..l28/145.8

Primary Examiner-Dennis E. Talbert, Jr. AttorneyDavid E. Dougherty and Robert E. Walter 57 ABSTRACT A fluidic control system for a filtering device employing a plurality of filters and means for causing a reverse flow through the filters to remove the impurities attached thereto. The control system acts to cause a plurality of rapid release valves to sequentially discharge a reservoir containing fluid under pressure into the filters as a predetermined pressure is attained in the reservoir. A time overridecontrol automatically advances the control system to a succeeding release valve if the previous release valve should fail to operate. The control system comprises pure fluidic components which operates without electrical or mechanical connections.

8 Claims, 7 Drawing Figures PAFENTEB MAY 2 9 I375 SHEET 1 0F 3 SHEET 2 OF 3 INVENTOR.

PATENTED HAY 2 9 I973 SHEET 3 OF 3 LLLLLLL} N) (D N hww mmm

A mw mm Mm%w CONTROL SYSTEM FOR A FILTERING APPARATUS BACKGROUND OF THE INVENTION In air filtering systems using reverse air flow for cleaning filter bags, a plurality of downwardly depending filter bags are normally used to separate the conveyor particles from the air medium. These filters require a periodical cleansing to release the material gathering on the outer sides thereof. Numerous systems utilize a high pressure back flow of blow down air from the output side to release the collected particles. Other systems more effectively utilize high volumes of low pressure air from a pressure reservoir to cleanse the fil ter structures.

Various control systems have been developed for sequentially discharging air through the bags to remove the impurities. One such system is described in U.S. Pat. No. 3,521,430 to Vanderlip et al. The control system disclosed therein employs air actuated spool or slide valves which have a movable spool piston. The spool piston moves in response to pressure differentials on either side thereof, thereby causing various ports to be opened or closed. The control valves operate to ac tuate a rapid release valve when a suitable pressure is obtained in a reservoir. The discharge of reservoir results in a cleansing action and causes the control valves to be actuated so that another rapid release valve is actuated when suitable pressure is again obtained in the reservoir.

In the aforementioned control system, the various mechanical control valves are subject to failure due to adverse conditions which might freeze or cause leakage of the valves. The filtering systems are often located outside where they are subjected to the adverse weather or inside flour mills, cement factories, and carbon black manufacturing industries, where the entrance of contaminated air into the control system may readily result in a failure thereof. A further disadvantage is that the sequential operation is dependent on the discharge of a rapid release valve or time base sequencing. If this fails to occur due to malfunction of a rapid release valve, the control system will not actuate a succeeding valve thereby resulting in a rapid decrease in efficiency of the whole filtering system. Also, since the control valves are actuated by a feed back pressure pulse from the rapid release valve control system must be located in close proximity to the filter system.

SUMMARY OF THE INVENTION It is an object of the present invention to obviate the above-mentioned deficiencies of prior control systems.

It is an object of the present invention to use a pure fluidic control system for operating a filtering system.

It is an object of the present invention to provide a time override system which automatically actuates another release valve when one release valve is inoperable.

Further and other objects of the present invention will become apparent upon reading the following description thereof.

In accordance with the present invention there is provided a control system for a filtering apparatus of the type comprising a plurality of filters, a reservoir for fluid under pressure, and means for discharging the reservoir for cleaning said filters, said control system comprising a means for sensing the pressure of the fluid in said reservoir, a fluidic means for sequencing a fluidic signal to actuate at least one of said discharging means in response to a predetermined pressure being assumed in said reservoir. There is also provided a timer means for actuating said sequencing means to advance the fluidic signal to at least one other discharging means after the reservoir maintains a discharge pressure for a predetermined period of time.

BRIEF DESCRIPTION OF THE DRAWINGS The following drawings which are illustrative of a preferred embodiment of the present invention are as follows:

FIG. 1 is a perspective view of the filtering apparatus;

FIG. 2 is a schematic illustration of the filtering apparatus;

FIG. 3 is a side elevational view in section of the rapid release valve;

FIG. 4 is a side elevational view in section of the pressure sensor;

FIG. 5 is a side elevational view in section of the fluidic amplifier;

FIG. 6 is a schematic drawing of the fluidic control system; and

FIG. 7 is a schematic drawing of a fluidic sequencing circuit using a decimal counter.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings in detail and in particular to FIG. 1, the air filtering apparatus, generally indicated at 11, has the control system 13 of the present invention connected thereto for the controlled operation and cleansing thereof. The air filtering apparatus 11 is generally used in pneumatic systems to separate granular material from air.

More specifically, the filtering apparatus 11 includes an enlarged airtight chamber 15 with an access door 17 mounted thereon. The access door 17 is pivotably connected by hinges to an enlarged opening and secured in the closed position as by conventional pressure lock members. An inlet conduit 19 is provided at a lower tapered portion of the chamber for a solids-laden gas. An outlet 21 at the bottom includes a valve 23 which acts to maintain pressure in the chamber 15 but permits the discharge of solids. An upper portion of the chamber 15 is separated from a lower portion as by separation plate 25 having a plurality of openings 27 therein in which are mounted, respectively, elongated filter bag assemblies 29. Above the separation plate 25 is a clean air plenum 31 having an outlet conduit 33 secured thereto for conveyance of fluid therefrom. Each of the filtering bag assemblies 29 is of a substantially conventional construction having an inner wire structure and a filtering bag of synthetic or woven wool material mounted thereon and secured thereto as by a clamp member. The filtering bags are of an elongated cylindrical shape operable to permit the passage of air therethrough. In normal operation of the air filtering means, pneumatic pressure conveys solids-laden gas into a lower portion of the chamber 15 whereby solids are deposited on the outside surfaces of the filter bags.

The frequent cleaning of the bag assemblies 29 is accomplished by a reverse flow of air from an outside source through the filtering bag to cause an air shock to remove material and particles contained thereon, which are discharged through the bottom outlet 21.

This air is supplied from a reservoir 35 in the form a large cylindrical type tank which is mounted on the forward side of the chamber. The reservoir is provided with an inlet conduit 37 connected to an air pressure supply source such as a motor driven blower or compressor.

A discharging means 41 includes a plurality of rapid release valves 43. Each release valve 43 has an inlet conduit 45 connected to the reservoir 35 and an outlet conduit 47 connected to downwardly depending dis charge tubes 49 extending within respective filter bag; assemblies 29.

As illustrated in FIG. 3 each rapid release valve includes a main housing 51 having an elongated enlarged vertical opening 53 with one end enclosed by an upper bell housing 55. The main housing 51 is further provided with the laterally extending conduits 45 and 47 which are respective inlet and outlet conduits. The valve 43 includes a piston assembly having a piston 61 with an outer surface in sliding engagement with the opening 53 and a central bore 63 adapted to receive a compression spring 65. The lower end of the spring 65 contacts the bottom of the main housing 51. Upward movement of the piston 61 under the force of the compression spring is limited by an inwardly extended flange portion 67 of a main housing 51. The piston 61 is machined of slightly smaller diameter than the opening 53 so that there is a fluid leakage to both sides thereof. The side wall of the main housing 51 is provided with an outlet opening 71 for exhausting fluid from the chamber formed by the piston 61 and the lower portion of the housing 51.

Each rapid release valve 43 is operable by pressure being supplied to both sides of the piston 61 creating an equilibrium condition with a rapid release of pressure through the bottom outlet 71 operating to cause a rapid downward movement of the piston 61 to quickly open the outlet conduit 47 to the inlet conduit 45.

The control device as illustrated in FIG. 5, comprises an amplifier means or portion 73 which is adapted to receive a fluid pressure signal of relatively low magnitude and cause an amplification thereof to a fluid pressure signal of sufficient strength to actuate a valve portion 75 of the control device. The valve portion 75 is connected to the rapid release valve 43 by a conduit 77 connected to outlet 71 thereby causing the exhausting of air from the lower portion of the rapid release valve 43 when the valve portion 73 is actuated.

The control device includes a cylindrical main housing 79 having a partition 81 therein separating the amplifier portion 73 from the valve portion 75. A central bore 83 extends axially through the partition 81 providing a passage from the amplifier portion 73 to the valve portion 75. In the amplifier portion 73 the central bore 83 has a constriction forming an opening 85 through a protruding portion of the partition 81. A diaphragm 91 which is in sealing engagement with the inside wall of the main housing 79 is in a plane substantially perpendicular to the central bore 83, and positioned so that the diaphragm 91 will close the opening 89 when pressure is exerted on the outside thereof.

An exhaust port 93 communicates with chamber formed between the diaphragm 91 and a partition 81. On the other side of the diaphragm 91 a chamber is formed with a cover plate 95 spaced from the diaphragm 91 and secured to the housing 79. The cover plate 95 includes an inlet 97 for a fluidic control signal which causes the diaphragm 91 to cover the opening A conduit 99 having an inlet port 101 exterior to the main housing 79 extends normal to the central bore 83 through the housing 79 and the partition 81 to communicate with the central bore 83. The inlet port 101 is connected to an air supply of suitable pressure. As illustrated in FIG. 6, the inlet port 101 is preferably connected directly to the reservoir 35 by bleed line 103.

The valve portion 75 includes a second partition 105 which is spaced from the partition 81 and has a central opening 107. A diaphragm member 109 which is positioned between the first 81 and second 105 partitions includes an axially aligned plunger 111 attached thereto extending through the opening 107. A spring 113 which is seated around the opening 107 is compressed between the diaphragm 109 and the second partition 105. The stem 115 of the plunger 111 which is connected to the diaphragm 109 is spaced from the central bore 83 and moves axially.

The stem 115 is connected at the other end to a head 117 which is disposed within an axially aligned conduit 119 extending outwardly from the valve portion 75. The conduit 119 includes a flanged portion tapered inwardly to form a central opening 123. The plunger head 117 is tapered outwardly to a cylindrical portion which matches the central opening 123. An O-ring fitted in a groove on the cylindrical portion provides for a sealing engagement of the head 117 with the central opening 123 as the plunger 111 is retracted. A plurality of radially extending exhaust ports 127 intermediate the second partition 105 and center opening 107 permits the exhausting of the bottom chamber of the rapid release valve 43 which is connected to the conduit 119 by a line 77.

The control system of the present invention is provided with a pressure sensing means or pressure sensor generally indicated at 131 and illustrated in FIG. 4. The sensing means 131 comprises a housing or body which is divided by a partition 135 into a lower section 137 for detecting pressure and an upper section 139 for generating a fluidic signal. Movably disposed within the lower section 137 is a movable piston 141. An inlet tube 143 has a passageway 145 communicating with the lower section 137 above the piston 141. The inlet 143 is connected to the reservoir 35 by a line 147.

A permanent magnet 149 is attached to the top of the piston 141. A coil spring 151 is provided for normally urging the piston 141 and magnet 149 toward the partition 135 so that the poles of the magnet are normally contiguous to the partition 135. Suitable sealing means 153 such as a diaphragm assure a tight fluid seal between the piston 141 and the housing to form a pressure chamber in the lower section 137.

In the upper section 139 there is disposed a fixed magnet 155 which has a center opening 157 and is spaced a predetermined distance above the partition 135. An armature 159 comprising a magnetically attractive material which is disc-shaped is positioned between the magnet 155 and the partition 135. The armature 159 moves between an upper and lower position in response to the movement of the piston 141. The armature 159 includes a peripheral flange and a center portion both of which project upwardly. The center portion is adapted to extend into the opening of the magnet 155 when the armature 159 is disposed in the upper position.

The upper section 139 includes an inlet port 165 and an exhaust port 167. The inlet port 165 is connected to a conduit having an orifice 171 positioned within the opening 157 of the fixed magnet. A diaphragm 173 extends over the opening 157 in sealing relationship thereto. With the armature 159 in the lower position, a spring 175 compressed between an upper wall and the diaphragm 173 forces the diaphragm 173 into the opening 157 and away from the orifice 171. The inlet port 165 is connected to a source supplying a continuous fluidic pressure signal by a T-connection so that opening the orifice 171 causes the fluidic signal to be exhausted or vented to the atmosphere through port 167. Closing the orifice 171 causes no exhausting so that a positive fluidic signal is transmitted.

in operation, with the piston 141 in the upward position the armature 159 is attracted to the permanent magnet 149 and the spring 151 urges the diaphragm 173 away from the orifice 171. When the pressure in the reservoir 35 reaches the predetermined value, preferably about 8 to about psi, the pressure in the lower section 137 is sufficient for the piston 14-1 to move downwardly against the force of the spring 151. The armature 159 is then away from the magnetic force of the permanent magnet 149 but becomes influenced by the force of the fixed magnet 155 which is sufficient to overcome the bias of the spring 175 and pull the armature 159 and diaphragm 173 upwardly to close the orifree 171 and cause a fluidic signal to be generated. When the pressure in the lower section 131 returns to a predetermined level the piston 141 returns to an upward position, the armature 159 returns to a lower'position the spring 175 opens the orifice 171, and the fluidic signal is terminated.

As herein described a one or a positive fluidic signal is a supply of fluid under pressure. A zero fluidic signal represents the absence of a supply of fluid under pressure. Preferably the fluidic signals are pneumatic.

The control system which is schematically illustrated in FIG. 6 includes standard fluidic components or elements. A plurality of NOR gates for generating fluidic signals are schematically represented by a shield symbol. Each gate has an output port at the head for the signal generated and control input ports at the base for receiving a control signal. The NOR gates operate to deliver a one signal at the output port in response to zero signals at all of the control ports and to deliver a zero signal in response to a one signal at any one of the control ports. The two-way sensors or relays 179 and 181 act to invert the signal received so as to convert a one signal to zero or vice versa. They comprise a diaphragm which moves in response to a one signal so as to interrupt a one signal from an external source thereby an inverted output signal.

Each of the fluidic control elements as described above are preferably supplied with clean control air from an external source (not shown). The connections between various fluidic elements are made with flexible tubing or molded channels. The aforementioned com- -ponents and their functional equivalents are wellknown in the prior art. It is intended that the following description of thecontrol circuit not be limited to specific control elements described but that various control elements may be conveniently used.

in general, in the preferred embodiment of the present invention the control circuit comprising fluidic control components is illustrated in FIG. 6 as comprising a plurality of fluidic circuits which are illustrated by the broken lines. A sequencing circuit or means 187 emits a fluidic signal which causes the plurality of discharging means to be actuated. A control circuit 189 is responsive to the pressure sensing means 131 and actuates the sequencing circuit 187. A timer circuit 191 overrides the control circuit 189 in the event a discharging means 41 fails to operate, and a display or indicating circuit 193 is provided to indicate the failure of a discharging means 41.

The sequencing means 187 which is preferably a flow brick circuit which may be obtained directly from Pitney-Bowes, part No. 6090 079. The sequencer 187 comprises a plurality of output ports 195. One of the ports 195 emits a one signal in response to zero input signal through the inhibit port 197. A one signal to the inhibit port 197 causes a zero signal at each of the ports 195. The fluidic signal is conveyed through one of a plurality of lines 199 connecting the output ports 195 to the amplifier means 73 which actuates the discharging means 411. The sequencer 187 advances to a succeeding or another of the output ports 195 when a one signal becomes a zero signal at the trigger port 201. The sequencer 187 is connected to a source of fluidic pressure.

The sequencing means 187 includes a reset port 203 which is connected to the output port of gate 205 which in turn has a control port connected to the output port of another gate 207. The latter gate 207 has a plurality of control ports, each of which is connected to one of the output ports 195 not in use. The reset port 293 is normally at a zero but in response to a one signal it automatically causes the sequencing means 187 to return to the first port 209 in the sequencing arrangement of ports 195. Thus, the generation of positive signals from the ports 195 is substantially confined to the output ports 195 which are illustrated as being connected to the plurality of amplifier means 73.

The control circuit 189 includes a relay 181 which receives a fluidic signal from the pressure sensor 131. The fluidic signal conveyed to the control port of gate 211 by the pressure sensor 131 is the inverse of the fluidic signal received by the relay 181. The output port of gate 211 is connected to the control port of gate 213 and to the trigger port 201. The output port of gate 213 is connected to the inhibit port 197 and to the control port of gate 215 of the timer circuit 191.

Connected with the aforementioned circuitry there is provided a timer means or circuit 191 which actuates the sequencer 187 in the event that the pressure in the reservoir remains at the discharge pressure for a predetermined time. The timer 191 comprises a gate 215 having a control port connected to the output of gate 213 of the control circuit 189. The output of gate 215 is connected by a line 217 having restriction 219 to a tank 221. A pressure sensor 223 which is commonly known as a three-way pressure sensor connects the tank 221 to the line 217 at a point between the restriction 219 and the output of gate 215. The tank or volume chamber 221 is connected to a relay 179. The output port of the relay 179 is connected to the control port of gate 227. The output port of gate 227 is connected to a filter circuit 229 and to gate 215.

The timer circuit 191 is a pulsating circuit. A zero signal at the control ports of gate 215 results in a posi tive fluidic signal in line 217 which is transmitted through restriction 219 and into tank 221. After a predetermined period of time sufficient pressure builds up in tank 221 to actuate relay 179 and cause the output port of relay 179 to go to zero. This results in output port of gate 227 becoming one, the output of gate 2155 becoming zero, and the fluidic signal in line 239 be coming zero. In response to a zero signal in line 239,

the pressure sensor 223 opens an exhaust port causing the pressure in tank 221 to go to zero. This latter even? results in the output of gate 215 emitting a positive sig nal which starts the cycle again unless a one signal from the output of gate 213 is transmitted to the control port of gate 215. The timer circuit is operable as a pulsating circuit so that an output signal from the sequencer will be advanced until an operable release valve 43 is actuated.

The filter circuit 229 filters out pulsations or irregularities in the fluidic signal and produces a filtered signal to the control input of gate 211 of the control cir cuit 189. The filter circuit 229 is a one shot circuit, which comprises a plurality of gates 231 and 233 each having a control port connected to the output port of gate 227. The output of one gate 231 is connected to a control port of the other gate 233 after passing through a sufficient length of inner connecting line 235 to modulate signal irregularities. The output of the gate 233 is then connected to the input of gate 211 of circuit 189 and to the control port of gate 243. When the timer circuit 191 causes the output port of gate 211 and the trigger port 201 to become zero the sequencer 187 advances to another port 195 without the necessity of a pressure drop in the tank 221.

A circuit 193 for indicating a malfunction is associated with the control system of the present invention. A line 241 connected to the output of the timer means 191 transmits a signal when the pressure reservoir 35 remains at a discharge level for an undue length of time. The line 241 is connected to gate 243 having an output port connected to gates 245 and 247. The output of the gate 245 is connected to a display device 249 of a conventional type art that is actuated by a fluidic signal. Gate 251 has a control port connected to the output port of gate 243 and an output port connected to the input port of gate 243. A one signal through the output port of gate 245 causes the display means or indicator 249 to be actuated and a one signal in the output port of gate 247 causes a remote indicator 248 to be actuated. This fluidic circuit has memory in that the malfunction is continuously displayed until a one signal to input port of gate 251 deactivates the display 249.

Actuation of a reset means generates a signal which removes thedisplay 249. As illustrated in the drawings, the reset means includes a manual switch 257 which is connected to the control port of gate 251. The output port of the manual switch 257 is connected to the input ports of gate 21 1 so that the trigger may be simultaneously actuated for manual sequencing.

According to another embodiment of the present invention, the sequencing means 187 as hereinbefore described comprises a decimal counter 259 interconnected with a plurality of buffer gates 261. The decimal counters 259 which are well-known in the prior art and are readily available comprise a plurality of output ports 263, a reset port 265 and a trigger port 267. A signal to the trigger port 267 causes the decimal counter to advance an output signal sequentially to another port 263.

The decimal counter illustrated in FIG. 7 is the type wherein all output ports 263 are one except the signal port which is zero. The zero signal is sequentially advanced to succeeding ports 263 by actuation of the trigger 267. Each output port 263 is connected to a buffer gate 261 which is in turn connected in a manner hereinbefore described to actuate the rapid release valve 43.

Connected to the control port of each buffer gate 261 is an inhibit line 269 which prevents an output signal from being generated until the proper pressure is obtained in the reservoir 35.

In operation, the control system of the present invention operates to actuate a rapid release valve 43 when a suitable discharge pressure is attained in the reservoir 35. When the reservoir 35 is not at the proper discharge pressure, the relay 181 receives a zero signal and emits a one signal to gate 211. Gate 211 in turn emits a zero signal to gate 213. Thus, the inhibit port 197 and the timer circuit 191 which are connected to the output port of gate 213 receive one signals so that all the filtering assemblies 29 are on the filtering cycle. When the pressure sensor 131 detects a predetermined discharge pressure in the reservoir 35, the relay 191 receives a one signal and emits a zero signal to gate 211 which emits a one signal to gate 213. This results in the one signal to trigger port 201 terminating thereby advancing the output of the sequencer 187 to another level or output port 195. Simultaneously, the one signal to the inhibit port 197 is terminated thereby causing a one fluidic signal to be emitted by one of the output ports 195. This latter signal actuates one of the discharging means 41 so that one of the filter assemblies 29 is cleaned by reverse air flow. As the pressure in the reservoir 35 decreases due to the discharge of fluid, the relay 181 again receives a zero signal at the input port and the one signals to the inhibit port and timer are resumed.

If for some reason the pressure in the reservoir 35 does not decrease, such as might be the case if the release valve 43 does not work properly, the fluidic signal to the trigger port 201 will remain at one. Thus, the reverse cleaning of the filter assemblies 29 is halted. in this case, the timer circuit 191 automatically emits a positive signal to the control means 189 causing the signal at the trigger 201 to go to zero. This advances the control system to the next port 195 so that the trouble is by-passed.

Also included in the circuit is an indicating means 183 for giving a warning when this latter event has occurred. This may be in the form of a visual display or a sound mechanism. It may be located in proximity to the fluidic circuit or located remotely. This device is designed to give an indication that there is a malfunction in the system. To return the indicating mechanism to its normal position an operator merely has to actuate a reset switch 257.

The control system of the present invention is operated by clean low pressure 'air being supplied to a plurality of fluidic logic elements. The control system may be operated or located remotely from the filtering apparatus. Since these filtering sites are usually or often times in locations which are subjected to adverse conditions such as dust, this latter feature can be conveniently employed.

Furthermore, a variety of reset and display means may be utilized with the present invention. Means are well-known for converting a fluidic signal which indicates a malfunction into electrical circuitry which may actuate a horn or flash a light. These automated features aid in providing an effective and efficient low cost means of providing automatic sequential cleansing of filter bags without excessive labor and without danger of explosion due to electrical spark in the light. This construction eliminates a great deal of time consuming and tedious work involved in replacing and cleansing filtering bags thereby achieving substantial time and monetary savings.

While the present invention has been described in conjunction with preferred embodiments thereof it should be understood that various modifications and changes therein would be obvious to one of ordinary skill in the art. It is intended that the aforementioned description of the preferred embodiments not limit the scope of the invention and that the claims'appended hereto include various changes and modifications therein.

What is claimed is:

l. A control system for a filtering apparatus of the type having a plurality of filter bags, a reservoir for fluid under pressure, means for rapidly discharging the fluid from said reservoir, said discharging means including a plurality of valves, each valve controlling the flow of fluid from said reservoir to at least one of said filter bags for the cleaning thereof with discharged fluid, wherein the improved control system comprises means for sensing the pressure of fluid in said reservoir, control means for generating a first fluidic signal in response to said sensing means detecting the predetermined pressure and a second fluidic signal in response to said first signal terminating, sequencing means including a plurality of output means, each output means adapted to convey an output fluidic signal to at least one of said valves for actuation thereof in response to the first signal, said sequencing means being operable to switch the output signal from one output means to another in response to said second signal, and timer means for producing the second signal in the event the second signal is not produced by said control means within a predetermined period of time.

2. A control system according to claim 1 including a display means responsive to the second fluidic signal from said timing means.

3. A control system according to claim 1 wherein the first signal terminates when the fluid under pressure is discharged from said reservoir.

4. A control system according to claim 1 comprising means for amplifying the output signal from an output means of said sequencing means to produce an amplified fluidic control signal, said amplifying means being adapted to convey said amplified fluidic control signal to at least one of said valves for actuation thereof.

5. A fluidic control system according to claim 1 wherein said discharging means comprises a rapid release valve having an inlet and an outlet, said inlet being connected to said reservoir, and a conduit connected to said outlet and having a plurality of discharge openings adjacent said filters to discharge fluid.

6. A fluidic control system according to claim 1 wherein said sequencing means includes a trigger means for advancing the output fluidic signal from one of said valves to another in response to said first fluidic signal being terminated.

7. A control system for a filtering apparatus of the type having a plurality of filter bags, a reservoir for fluid under pressure, a plurality of rapid release valves having an inlet and an outlet, said inlet being connected to said reservoir, and a conduit connected to said outlet having a plurality of discharge openings adjacent said filter bags to discharge fluid, wherein the improved control system comprises means for sensing the pressure of fluid in said reservoir, control means for generating a first fluidic signal in response to said sensing means detecting the predetermined pressure and a second fluidic signal in response to said first signal terminating, said first signal terminating when the fluid under pressure is discharged from said reservoir, sequencing means including a plurality of output means, each output means being connected to and adapted to convey an output fluidic signal for actuation of at least one of said valves in response to the first signal, said sequencing means including trigger means operable to switch the output signal from one output means to another in response to said second signal, means for amplifying the output signal from an output means of said sequencing means to produce an amplified fluidic control signal, said amplifying means being adapted to convey said amplified fluidic control signal to at least one of said valves for actuation thereof, and timer means for producing the second signal in the event the second signal is not produced by said control means within a predetermined period of time.

8. A control system according to claim 7 including a display means responsive to the second fluidic signal from said timing means. 

1. A control system for a filtering apparatus of the type having a plurality of filter bags, a reservoir for fluid under pressure, means for rapidly discharging the fluid from said reservoir, said discharging means including a plurality of valves, each valve controlling the flow of fluid from said reservoir to at least one of said filter bags for the cleaning thereof with discharged fluid, wherein the improved control system comprises means for sensing the pressure of fluid in said reservoir, control means for generating a first fluidic signal in response to said sensing means detecting the predetermined pressure and a second fluidic signal in response to said first signal terminating, sequencing means including a plurality of output means, each output means adapted to convey an output fluidic signal to at least one of said valves for actuation thereof in response to the first signal, said sequencing means being operable to switch the output signal from one output means to another in response to said second signal, and timer means for producing the second signal in the event the second signal is not produced by said control means within a predetermined period of time.
 2. A control system according to claim 1 including a display means responsive to the second fluidic signal from said timing means.
 3. A control system according to claim 1 wherein the first signal terminates when the fluid under pressure is discharged from said reservoir.
 4. A control system according to claim 1 comprising means for amplifying the output signal from an output means of said sequencing means to produce an amplified fluidic control signal, said amplifying means being adapted to convey said amplified fluidic control signal to at least one of said valves for actuation thereof.
 5. A fluidic control system according to claim 1 wherein said discharging means comprises a rapid release valve having an inlet and an outlet, said inlet being connected to said reservoir, and a conduit connected to said outlet and having a plurality of discharge openings adjacent said filters to discharge fluid.
 6. A fluidic control system according to claim 1 wherein said sequencing means includes a trigger means for advancing the output fluidic signal from one of said valves to another in response to sAid first fluidic signal being terminated.
 7. A control system for a filtering apparatus of the type having a plurality of filter bags, a reservoir for fluid under pressure, a plurality of rapid release valves having an inlet and an outlet, said inlet being connected to said reservoir, and a conduit connected to said outlet having a plurality of discharge openings adjacent said filter bags to discharge fluid, wherein the improved control system comprises means for sensing the pressure of fluid in said reservoir, control means for generating a first fluidic signal in response to said sensing means detecting the predetermined pressure and a second fluidic signal in response to said first signal terminating, said first signal terminating when the fluid under pressure is discharged from said reservoir, sequencing means including a plurality of output means, each output means being connected to and adapted to convey an output fluidic signal for actuation of at least one of said valves in response to the first signal, said sequencing means including trigger means operable to switch the output signal from one output means to another in response to said second signal, means for amplifying the output signal from an output means of said sequencing means to produce an amplified fluidic control signal, said amplifying means being adapted to convey said amplified fluidic control signal to at least one of said valves for actuation thereof, and timer means for producing the second signal in the event the second signal is not produced by said control means within a predetermined period of time.
 8. A control system according to claim 7 including a display means responsive to the second fluidic signal from said timing means. 